This invention relates to a coaxial connector assembly.
Electronic signal processing and routing equipment, such as that used in the professional broadcast industry, requires a means for delivering signals to, and receiving signals from, the equipment. Typically, this requirement is met by signal connectors projecting from a back panel of the equipment, where cables provided with mating connectors can be engaged with the equipment connectors.
As the capability of electronic signal processing and routing equipment to handle multiple signals has increased, the desire to take advantage of that capability has led to an increase in the number of connectors projecting from the back panel of the equipment, such that the physical dimensions of the equipment can be dictated not by the bulk of the interior functional components of the equipment but by the need to have a back panel large enough to accommodate all the connectors that can be served by the interior functional components.
A connector that is commonly used in the professional broadcast and other industries is the BNC connector. The BNC connector is composed of a receptacle and a plug. The receptacle includes a ground conductor in the form of a hollow cylindrical barrel and a signal conductor that extends axially within the barrel. The barrel of the BNC receptacle is electrically connected to a ground plane conductor of a PCB backplane and the center conductor is electrically connected to a signal trace of the PCB backplane. The barrel has an axially outer portion with an external surface that is essentially smooth, except for bayonet pins that project from the smooth external surface in order to engage corresponding slots in a shroud of the BNC plug, and an axially inner portion provided with an eternal screw thread. The external diameter of the axially outer portion of the barrel is 9.5 mm. Typically, the plug includes a dielectric housing, and the external diameter of the housing places a lower limit on center-to-center spacing of receptacles in a field of receptacles. In practice, the lower limit is currently 0.625 inches (15.875 mm).
The back panel of electronic equipment normally includes a metal back plate overlying the PCB backplane. The metal plate is grounded and forms part of the EMI shielding for the equipment. Further, the metal plate is stiff and provides dimensional stability to the equipment""s enclosure. Generally, the BNC receptacles are positioned so that the barrels extend through respective holes in the metal plate.
It is necessary that the BNC receptacle be attached firmly to the back panel of the equipment in order to ensure that the electrical connections to the PCB backplane, which are typically effected by soldering, will not be disrupted during normal use, which may involve applying axial, transverse and rotational forces to the barrel. In some cases, the receptacle can be soldered into the PCB backplane assembly with sufficient retention to provide a robust connection, in which case the barrel may extend loosely through the hole in the back plate. In other cases, it is not possible to provide a sufficiently robust soldered connection, and it is then necessary to retain the receptacle by clamping the back plate between an exterior flange of the receptacle on the inner side of the back plate and a separate fastening element, specifically a nut in threaded engagement with the barrel, on the outer side of the back plate. Hitherto, it has been conventional to employ a standard hexagonal nut for this purpose. It is, however, difficult or impossible to install a standard hexagonal nut using a conventional socket or wrench, which engages flats at the periphery of the nut, when the barrels of the BNCs are at a center-to-center spacing as small as 0.625 inches because there is not sufficient space between adjacent nuts to accommodate the tool. Consequently, as a practical matter, use of BNC connectors at the minimum spacing has hitherto been confined to equipment in which the BNCs can be secured without a separate fastening element.
In accordance with the invention there is provided a coaxial connector assembly for mounting in an aperture in a stiff plate, said connector assembly including a barrel having a forward end for receiving a mating connector, a shoulder at a rear end for engaging an interior surface of the mounting plate, and an external screw thread intermediate the front and rear ends of the barrel, and a nut which can be fitted on the barrel from the forward end thereof and has an internal screw thread for threaded engagement with the external screw thread of the barrel, and wherein the nut has an end face with a key formation for engagement by a driving tool.